“While the facts and circumstances are still evolving, especially with respect to why this customer defied Chicago Aviation Security Officers the way he did, to give you a clearer picture of what transpired, I’ve included below a recap from the preliminary reports filed by our employees,” Munoz wrote.

Munoz acknowledged “there are lessons we can learn from this experience,” and admonishes employees to treat customers “with respect and dignity.” But he gives no hint that the airline did anything wrong.

The email included a five-point summary of what transpired, based on reports by company employees. Munoz said United staff asked passengers to volunteer to get off the plane after airline crew members arrived at the gate and “needed to board the flight.” Too few passengers volunteered, so the airline invoked its “involuntary denial boarding process,” he said.

Airline workers called security officers after the passenger repeatedly refused to get off the plane and became “more and more disruptive and belligerent,” Munoz wrote.

“Our employees followed established procedures for dealing with situations like this,” Munoz wrote. “While I deeply regret this situation arose, I also emphatically stand behind all of you, and I want to commend you for continuing to go above and beyond to ensure we fly safe.

“I do, however, believe there are lessons we can learn from this experience, and we are taking a close look at the circumstances surrounding this incident,” he added. “Treating our customers and each other with respect and dignity is at the core of who we are, and we must always remember this no matter how challenging the situation.”

Munoz released a statement earlier Monday in which he apologized for having to “re-accommodate these customers.”